You might also hear this as a capital and interest mortgage.
A repayment mortgage is where your monthly mortgage repayments pay off both the principal (the loan amount, also called capital) and the interest at the same time, rather than just the interest, which you would on an interest only mortgage.
It is the most common type of mortgage, and suitable for most people.
You might be able to pay more than your set monthly repayment figure, often called overpaying. This extra money would reduce the loan amount further and therefore reduce the amount of interest you pay over the life of the mortgage.
Learn more about overpaying and mortgages here.